Cutback bitumen is a combination of bitumen and a solvent, such as kerosene or gasoline, that is suitable for the intended purpose. The type and quality of Cutback bitumen depend on the quality of the original pure bitumen, the type of solvent, and the amount of solvent used. Cutback bitumen is commonly used in road construction for surface coatings, infiltration, cold factory asphalt, and on-site mixes.
Different Types of Cutback Bitumen Based on Their Curing Time
There are three types of cutback bitumen based on the rate of solvent evaporation or drying time.
Rapid Curing Bitumen (RC):
Due to the high rate of gasoline evaporation, the bitumen in gasoline hardens faster. This bitumen is called rapid curing bitumen (RC) . The solvents used in this type of bitumen evaporate at a rate 0.3 times faster than that of acetone. Rapid-curing grades of RC are commonly utilized for tack coats, chips seals, and sand seals.
Medium Curing Bitumen (MC):
Bitumen dissolved in kerosene are called medium curing bitumen, which has a slower and longer evaporation rate than gasoline.
Slow Curing Bitumen (SC):
Slow curing bitumen is prepared by dissolving penetration bitumen with heavy distillate solvents. Their evaporation rate is 0.8 times lower than the evaporation rate of acetone.
Cutback Bitumen Advantages
Cutback bitumen has several advantages and benefits, making it an invaluable resource across various industries. Some of the key benefits of cutback bitumen are:
- Workability: Cutback bitumen has improved workability as compared to standard bitumen. The added solvent reduces viscosity, making it easier to spray or spread, and allowing it to be used at lower temperatures.
- Versatility: Cutback bitumen can be tailored to suit specific needs by adjusting the type and amount of solvent used. Rapid-curing cutbacks use lighter solvents and cure quickly, while medium and slow-curing cutbacks use heavier solvents and take longer to cure.
- Strong Adhesive Property: Cutback bitumen serves as a strong adhesive, making it excellent for binding aggregates in road construction.
- Resistance to Weather Conditions: Once the solvent has evaporated and the bitumen has hardened, it forms a resilient, waterproof layer that can withstand a variety of adverse weather conditions.
- Flexibility: Despite its toughness, cutback bitumen retains a level of flexibility, enabling it to tolerate surface shifts or temperature changes without cracking.
- Durability: Structures made with cutback bitumen can last for many years when properly applied, making it a cost-effective choice for many projects.
Common Cutback Bitumen Grades and Their Uses
The choice of cutback bitumen grade depends on the specific application and desired performance criteria, such as curing time, viscosity, and temperature range. Here are the different grades of cutback bitumen and their uses:
- Cutback Bitumen MC30: This grade is ideal for use as a thin coating called a prime coat, which is applied to the base course of a road before laying the asphalt layer. It can also be used as a tack coat, which is applied to an existing road surface before applying a new asphalt layer.
- Cutback Bitumen MC70: This grade is similar to MC30, but it has a higher viscosity, making it suitable for use in lower temperatures. It is also used as a prime and tack coat.
- Cutback Bitumen MC250: This grade has a higher viscosity than MC70 and is used for sealing and waterproofing applications.
- Cutback Bitumen RC30: This grade cures quickly and is used for tasks that require a substance that dries fast, such as patching and repair work.
- Cutback Bitumen RC70: This grade cures quickly as well and is used for repairing and maintenance work, as well as the construction of temporary roadways.
- Cutback Bitumen RC250: This grade cures quickly and is used for patching and repair work, as well as the construction of temporary roadways.
- Cutback Bitumen SC70: This grade cures slowly and is used in situations where a longer curing period is necessary, such as the construction of airport runways and other high-stress applications.
- Cutback Bitumen SC250: This is also a slow-curing grade of cutback bitumen and is used in situations where a longer curing period is necessary, such as the construction of airport runways and other high-stress applications.